1. Field of the Invention
This invention relates to a method of automatically controlling mixing of two kinds of fuel oil at a desired ratio, and more particularly to a fuel oil mixing method of mixing a low grade oil (for example, Heavy Fuel Oil) with a high grade oil (for example, Diesel Oil), between which oils there is a substantial temperature difference prior to mixing, at a desired ratio, and continuously feeding the mixture as mixed fuel to a diesel engine, gas turbine, boiler or the like.
This invention relates also to a method of controlling the mixing speed in performing the above mixing method.
2. Prior Art
Included under the method of mixing the fuel oils of the kind described above for use in marine engines, boilers, etc. are those methods shown in FIGS. 1(a) to 1(c), of which a method (a) includes metering pumps 4, 5 disposed through strainers 3, 3 in the midway of feed passageways 1, 2 for fuel oils A and B (check valves are indicated by the numeral 10), a method (b) is designed to control two oils A and B at a specified ratio by disposing rate of flow transmitters 6, 7 in the passageways 1, 2 and inputting pulses from the transmitters 6, 7 into an automatic controller 8 to control a flow control valve 9 disposed in one passageway 1 by output from the controller 8 to control two oils A and B at a specified ratio of mixing (the numeral 3 designates strainers and 10 designates check valves), and a method (c) is intended to mix the oils by variable speed pumps 12, 12 being driven by variable speed motors 11, 11.
By the way, on account of the recent inclination of the use of fuel toward low grade oil by reduction in fuel cost and on account of restrictions on conditions of injecting of the highly refined fuel, the supply temperature of the low grade oil is needed to increase and is heated to 120.degree.-140.degree. C., while on the other hand, high grade oil has low viscosity and much volatile matter, so that it is stored at room temperature of 25.degree. to 40.degree. C. to be fed to engines. Accordingly, from the viewpoint of operational control of the engine, high grade fuel oil is used in time of starting the engine, and is changed over to low grade fuel oil at a suitable time after warm-up to enter into continuous operation and is again changed over to high grade oil before stopping the engine. The changeover operation described above has provided a hindrance to automatic operation of the engine in that it demands the use of experience and knack on the part of the operator because there is a great difference in temperature between the two oils and sudden changeover between the oils tends to cause thermal shock.